Chaotic approach to control of lighting

ABSTRACT

At least one controllable source of visible light is configured to illuminate a space to be utilized by one or more occupants. A controller causes the source(s) to emit light in a manner that varies at least one characteristic of visible light emitted into the space over a period of time at least in part in accordance with a chaotic function.

RELATED APPLICATION

This application is related to U.S. Utility patent application Ser. No.13/594,236 Filed Aug. 24, 2012 entitled “ENVIRONMENTAL CONTROL USING ACHAOTIC FUNCTION,” the disclosure of which is entirely incorporatedherein by reference.

TECHNICAL FIELD

The present subject matter relates to techniques and equipment tocontrol one or more characteristics of lighting utilizing a chaoticfunction.

BACKGROUND

Electrical lighting has become commonplace in modern society. Electricallighting devices are commonly deployed, for example, in homes andbuildings of commercial and other enterprise establishments. Traditionalgeneral lighting devices have tended to be relatively dumb, in that theycan be turned ON and OFF, and in some cases may be dimmed, usually inresponse to user activation of a relatively simple input device. Suchlighting devices have also been controlled in response to ambient lightdetectors that turn on a light only when ambient light is at or below athreshold (e.g. as the sun goes down) and in response to occupancysensors (e.g. to turn on light when a room is occupied and to turn thelight off when the room is no longer occupied for some period). Oftensuch devices are controlled individually or as relatively small groupsat separate locations.

With the advent of modern electronics has come advancement both in thetypes of light sources and in the control capabilities of the lightingdevices. For example, solid state sources are now becoming acommercially viable alternative to traditional light sources such asincandescent and fluorescent lamps. By nature, solid state light sourcessuch as light emitting diodes (LEDs) and organic LEDs (OLEDs) are easilycontrolled by electronic logic circuits or processors. For example, manyfixtures or systems using solid state light sources enable control ofboth intensity and color characteristics of the overall light output.Electronic controls have also been developed for other types of lightsources.

Traditional control algorithms involved setting a condition or parameterof the light output, such as intensity and/or color and then maintainingthe set condition within some minimal variance for a relatively longperiod of time, e.g. over a work day or a period occupancy. Advancedelectronics in the control elements, however, have facilitated moresophisticated control algorithms. For example, some systems have beenconfigured to vary a condition of lighting in accordance with acircadian rhythm. A circadian rhythm is a biological function thatcorresponds to a natural 24 hour cycle. For lighting purposes, lightingin an office or the like has been controlled in a manner to simulatevariations of natural daylight over some portion of the daytime duringwhich the office is expected to be occupied, so as to simulate thatportion of the natural 24 hour cycle of sunlight.

Control algorithms based in whole in part on a circadian rhythm may helpto promote harmony of the occupants with the lighted environment.However, such algorithms are still somewhat limited in that they tend tofollow a general trend, such as average intensity of daylight, over therelevant period of the day.

The Fraunhofer Institute developed a Virtual Sky® in the form of aceiling grid that was illuminated to appear as a moving sky withvariable light intensity and sky colors. However, this approach isessentially an emulation of a natural environmental condition notspecifically configured to manipulate the environment to influence anoccupant's sense of being. Also, such a lighting grid is far too complexand expensive for wide adoption in environments for typical spacesintended for human occupancy, such as homes, offices, agriculturalbuildings, commercial buildings or the like.

Other types of lighting have been controlled in response to variousconditions or inputs, for example, in response to music. At least somemusical sound may be considered chaotic. However, lighting in responseto or coordinated with music has been intended for special effectslighting or entertainment and not for control of general lighting suchas task lighting in an enterprise or residential space.

Hence, there is room for still further improvement in a lighting controlalgorithm to better promote an objective purpose of an illuminated areaor space when occupied, and/or which can be implemented using devices orsystems for general lighting that are readily adaptable to environmentsfor typical spaces, such as homes, offices, agricultural buildings,commercial buildings or the like.

SUMMARY

The concepts disclosed herein improve controlled lighting by introducingcontrolled variation of one or more characteristics of light in achaotic manner.

In the examples discussed below, a lighting device includes at least onecontrollable source of visible light, to illuminate a space to beutilized by one or more biological occupants. A controller is coupled tothe source or sources to control operation thereof. The operationalcontrol causes the source(s) to emit light in a manner that varies atleast one characteristic of visible light emitted into the space over aperiod of time at least in part in accordance with a chaotic function.

Many natural environmental conditions, including natural lighting, arechaotic systems. The human nervous system is a chaotic system, which isat least somewhat attuned to chaotic inputs from the naturalenvironment. Adding a chaotic variation to lighting of an inhabitedspace or region, as in the examples discussed in the detaileddescription, may help to liven up or put life (dynamic change) in thelighting of the space or region, as perceived by a person occupying thespace. For example, the variation in lighting may effect perception byan occupant in a manner that promotes an objective purpose of the space,although the variation may or may not mimic naturally occurringvariations in daylight. The impact of the chaotic functional controloften is positive; but under some circumstances, the impact may benegative, e.g. to discomfort an unwanted visitor or intruder. In thespecific examples, the expected occupants are human; however, thetechnologies discussed in the examples may be applied to controllighting of spaces intended for other biological occupants in additionto or instead of humans.

The examples described in more detail below include individual lightfixtures as well as lighting systems utilizing a number of fixtures orother types of lighting devices, configured to implement chaoticfunction control of the type discussed herein. The concepts may beimplemented in new light fixtures, devices or systems. Alternatively,the chaotic function control may be retrofitted into an existing device,fixture or system, for example, by updating the control program for therelevant controller(s), in which case relevant control functions may beembodied in programming.

The examples described below also encompass methods. Such a method mayinvolve operating an electrically driven source to produce visiblelight, to illuminate a space to be utilized by one or more biologicaloccupants. The operating step is controlled so as to vary at least onecharacteristic of the visible light from the source over a period oftime at least in part in accordance with a chaotic function.

Additional objects, advantages and novel features of the examples willbe set forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing and the accompanying drawings or may be learned by productionor operation of the examples. The objects and advantages of the presentsubject matter may be realized and attained by means of themethodologies, instrumentalities and combinations particularly pointedout in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present concepts, by way of example only, not by way of limitations.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1 is a simplified diagram showing an example of a number oflighting devices illuminating a space to be utilized by one or moreoccupants, where the lighting devices are configured to vary operationof the light source(s) so as to vary at least one characteristic ofvisible light emitted into the space over a period of time at least inpart in accordance with a chaotic function.

FIG. 2 is a graph showing a relationship of states of a variable to arange of coefficient values for an equation that may define a chaoticcontrol function, for a simple example.

FIGS. 3A to 3E show the resulting functions, achieved using differentvalues for the coefficient, for the equation represented in FIG. 2.

FIGS. 4A to 4C, respectively show a chaotic function in anunstable-with-attractors state, a portion of a sine wave and an exampleof a combination of the chaotic function and the sine wave portion.

FIG. 5A illustrates a rough approximation of a general trend or nominalcurve for natural sunlight, from dawn to dusk.

FIG. 5B shows an example of an approximate nominal curve for colortemperature for natural sunlight, over the hours of daylight.

FIGS. 6A to 6C, respectively show the chaotic function in theunstable-with-attractors state, another chaotic function in a similarstate but using a different timing rate and an example of a combinationof the two chaotic functions.

FIG. 7 depicts an example of the two-chaotic example of FIG. 6C combinedtogether with a portion of a sine wave.

FIGS. 8A to 8C are graphs of light condition measurements, specificallyflux, color temperature and chromaticity difference (Delta_uv), for asunny day.

FIGS. 9A to 9C are graphs of light condition measurements, specificallyflux, color temperature and chromaticity difference (Delta_uv), for acloudy day.

FIG. 10 is a functional block diagram of a system of light fixturesutilizing network communication.

FIG. 11 is a somewhat more detailed block diagram of an example of alight fixture that may be used in the system of FIG. 1 or the system ofFIG. 10.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may, be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The various examples disclosed herein relate to lighting devices,fixtures or systems and ways to control such equipment to providecontrolled variation of one or more characteristics of emitted light ina chaotic manner. Reference now is made in detail to the examplesillustrated in the accompanying drawings and discussed below.

FIG. 1 illustrates a simple first example. The drawing shows a region orspace 1, which is intended to be utilized by one or more occupants 2. Inthe specific example, the occupants shown are human. However, thelighting control technology may be applied to light spaces intended forother biological occupants in addition to or instead of humans. Forpurposes of illustration and further discussion of the examples, we willassume human occupancy. The space 1, for example, may be a room in abuilding; although the lighting techniques under consideration here maybe applied to any indoor or outdoor region or space that requires atleast some artificial lighting. The lighting equipment involved hereprovides the main artificial illumination component in the space, ratherthan ancillary light output as might be provided by a display, or by orin association with a sound system, or the like. As such, theillumination from the fixtures, lamps or other elements controlled inaccordance with a chaotic function is the main artificial illuminationthat supports the purpose of the space, for example, the lighting thatalone or in combination with natural lighting provides light sufficientto allow occupants in the space to perform the normally expected task ortasks associated with the planned usage of the space. Often, suchlighting is referred to as “general” lighting.

Human habitation often requires augmentation of natural ambient lightingwith artificial lighting. For example, many office spaces, commercialspaces and/or manufacturing spaces require task lighting even whensubstantial amounts of natural ambient lighting are available. For manyof these uses, the level of the light may be specified by one or moreregulatory authorities. Hence, when natural ambient light is available,ambient and task lighting should be integrated such that they do notwork against one another. For example, natural ambient lighting shouldnot be distracting to the task(s) to be performed in the lighted space.An example is discussed later that utilizes ambient light sensing, thatincludes sensing of any natural ambient light or the like that may beavailable, to adjust the control of the artificial lighting device(s).Ambient light sensing detects at least some light that is present in thespace even if the controlled artificial lighting were absent or turnedOFF; although depending on the sensor/detector configuration, some ofthe controlled artificial lighting may also be detected. For ease ofillustration and discussion, however, this initial example assumes onlyartificial lighting.

Hence, in our first example, the space 1 is an enclosed room or the likeand is shown without windows or any other means of providing daylightingfrom an exterior of the building to the room space 1. In many actualinstallations, the space will include a window, skylight or otherdaylighting device configured to allow some amount of sunlight to enterthe space. However, for its intended purpose or usage, the spacerequires at least some artificial lighting. Hence, the space 1 can beilluminated as/when desirable by at least one lighting device thatproduces artificial light during at least some times of occupancy.

The lighting device could be a table or floor lamp, etc.; although inour example, the space is illuminated by a number of light fixtures 3.Each light fixture 3 includes one or more controllable sources 4 ofvisible light, for illumination of the space 1. The example shows thefixtures 3 mounted in the ceiling and oriented so that the lightemissions from sources 4 are directed generally downward into the space1. Such a downlight configuration, for task lighting or other similarillumination applications, is exemplary only. The fixtures or othertypes of lighting devices in the example may be at any location and/ororientation relative to the space and the expected occupants 2 tosupport a desired general lighting application appropriate for the usageor purpose intended for the space 1. For example, the downlight fixtures3 provide direct lighting from above. As other examples, indirectlighting may reflect light off of a ceiling or wall surface or thelighting may principally illuminate an object in the room to be viewedby the occupants 2. Each source 4 may be implemented with any suitablelight generation device; although specific examples discussed belowutilize LEDs alone or in combination with other sources, such asincandescent, fluorescent or organic LED (OLED) lamps and daylighting.

The sources 4 are controlled by one or more controllers. In anintegrated system, for example, there may be one controller for allsources that artificially illuminate the space 1. In this first example,each light fixture 3 also includes a controller 5 coupled to the sourceor sources 4 in the fixture 3, to control operation thereof. Theoperational control causes the source(s) 4 to emit light in a mannerthat varies at least one characteristic of visible light emitted intothe space over a period of time at least in part in accordance with achaotic function. Some or all of the chaotic variation(s) may often notbe consciously perceptible by an occupant of the space; however,sub-conscious perception of the chaotic variation(s) may still impactthe occupant's perception of the environment in the space.

The lighting device, for example each of the light fixtures 3 in FIG. 1,uses power to run the controller 5 and drive the source(s) 4 to emitlight. In the example, each light fixture draws electrical power fromalternating current (AC) mains 6, although the light fixture 3 may bedriven by a battery or other power source under normal conditions or inthe event of a failure of AC mains power 6.

In the example, the light fixtures 3 are responsive to control inputfrom a user interface device 7. The user interface device 7 can be asimple ON-OFF switch or a dimmer; or the user interface device 7 may bea more sophisticated digital control and data entry/output device. Whenthe fixtures 3 are turned ON in response to the input from the userinterface device 7, the controllers 5 generally set the output intensityto a general level and may maintain one or more color characteristics atset values. If the user interface device 7 merely provides ON-OFFsettings, then the intensity and any other controlled characteristicswould be maintained at around programmed nominal settings. If theinterface device 7 provides dimming control for the user, then thecontrollers 5 would reduce the output intensity from the full ON settingto an intensity corresponding to the dimmer setting. The controllers mayalso set one or more color characteristics in a similar manner inresponse to user inputs via the device 7. However, each controller 5 inthe example is also configured to vary one or more of the lightingcharacteristics from the nominal settings, including from any settingsinput via the user interface device 7, over a period of time, at leastin part in accordance with a chaotic function.

Where there are a number of lighting devices that illuminate the space1, such as light fixtures 3 in this example, the intent is for the totalillumination in the space 1 to exhibit chaotic behavior in the intendedmanner. To that end, chaotic variations among fixtures 3 may be in-phasewith each other (same timing), for example, if there is synchronismand/or common control for the fixtures 3. Alternatively, operations ofone or more of the fixtures 3 may be phase delayed relative to otherfixture(s) to produce similar variations but different/delayed timings;or the various fixtures 3 may be running independently and thereforeproducing independent chaotic components (out of phase and withdifferent variations). Other installations may be arranged with one ormore lighting devices implementing the chaotic function control whereasone or more lighting devices may not implement the chaotic functioncontrol.

The chaotic functional control or variation of the light characteristicsmay be implemented using a variety of control algorithms. It may beuseful at this point in the discussion to consider chaotic functions inmore detail, both in general terms and in terms of application thereofto control of a lighting device or system.

In science and mathematics, chaos is not a lack of order. To thecontrary, chaos is an apparent lack of order in the outcomes of acomplex dynamic system that actually may be deterministic. A chaoticsystem often is deterministic in that it follows one or more rules;however, system results are unpredictable and appear random or lackingin order because the results are not readily predictable, particularlyin the long run. Hence, a chaotic system is one that operates in adynamic manner and its dynamic operations are highly sensitive toinitial conditions. The outcomes at a point in time are often determinedby the parameters occurring at one or more preceding points in time,which serve as the inputs to the deterministic system in driving thecurrent outcomes. Sensitivity to initial conditions means that smalldifferences of initial conditions can yield significantly differentresults. In a system that depends on prior conditions, the priorconditions become the inputs for current or future determined outcomes;therefore such a chaotic system tends to be highly sensitive to theconditions leading up to current time. The sensitivity to initialconditions, say the current and prior conditions that serve as ‘initialconditions’ for prediction of future outputs, makes prediction oflong-term outcomes difficult or impossible.

Chaotic behavior occurs in many natural systems. Weather, for example,is a naturally occurring chaotic system. It is relatively easy toobserve present conditions and track past conditions, for use inpredicting the weather. However, even with sophisticated computermodeling and increasingly comprehensive data accumulation, weather isnot readily predictable beyond a few days or a week. Examples of thechaotically varying characteristics of the weather include conditionslike air temperature, air pressure, humidity, precipitation, visibility,wind speed, and wind direction (in two or three dimensions).

In an outdoor environment, parameters of natural lighting produced bysunlight, shading and/or reflection of light in the environment andlight transmission through the atmosphere also form a naturallyoccurring chaotic system. Examples of the chaotically varyingcharacteristics of naturally occurring lighting include intensity oflight flux, color temperature of the light and chromaticity differenceor Delta_uv (distance of color characteristic point off of the Planckianlocus, in uv color space).

The human nervous system also is a chaotic system. However, aspects ofhuman perception are, after eons of evolution in Earth's naturalenvironment, accustomed and even somewhat attuned to natural variationof characteristics of the environmental conditions, includingchaotically varying characteristics such as those of the weather and ofnatural lighting. As a result, humans are actually sensitive tovariations, including chaotic variations at levels and rates that maynot be readily or consciously perceptible. However, sensing of suchvariations does impact the human nervous system in ways that may affecthuman mood and/or performance. Compared to natural conditions,controlled characteristics of indoor conditions have tended in the pastto be relatively static over substantial periods of time each day.

The systems and procedures discussed below by way of examplesincorporate chaotic variations into control functions of a lightingdevice or system in a manner intended to support or facilitate anobjective purpose of a space that the device or system illuminates.Depending on the purpose(s) of the space, the environment in acontrolled space can calm, the environment can excite, the environmentcan affect productivity favorably or unfavorably, and/or the environmentcan make occupants feel good, bad or indifferent. For many applications,promotion of the purpose of the space will involve a lighting effectthat may be considered positive or pleasant in some manner. However, forsome purposes and/or at some times, a negative or unpleasant impact maybe appropriate, e.g. to encourage unwanted visitors (human or animal orinsect, etc.) to leave a space or even to impair an intruder'sperception while intruding into a secure space.

The chaotic variation of a light characteristic introduced by thetechnologies discussed herein may be similar to that found in nature;however, the lighting control need not particularly mimic natural daylighting. In many settings, the variation need not track that occurringin nature. Rather than implementing natural day lighting conditions inthe illuminated space, for at least those purposes where aspects ofdaylight support the intended purpose, the controlled lighting system ordevice adds analogous components via chaotic function control, to livenup or put life (dynamic change) in one or more of the characteristics ofthe lighting condition in the space illuminated by the device or system.

Some examples of chaotic functions may be defined by three or morelinked differential equations, often where each equation has one or morenon-linear terms and the coefficients of the terms configure the systemof equations for operation near or at a transition point from orderly todisorderly behavior. However, other formulae may be used. A somewhatsimpler chaotic function maybe expressed by an equation like thefollowing:x _(n+1) =rx _(n)(1−x _(n))  (1)

(Source: Wikipedia, “Chaos Theory,”http://en.wikipedia.org/wiki/Chaos_theory)

In equation 1 above, the variable x for the next time point n+1 isdependent on the value of x of the current time point n. The initialcondition for x_(n+1) is x_(n). FIG. 2 is a graph (from the sourceWikipedia article noted above) showing possible outcomes of x fordifferent values of the coefficient r. The example uses a damping typeof equation that creates a chaotic function.

For values of r below approximately 3.0, x is a relatively monotonicfunction. FIG. 3A shows the function x_(n+1), for a range to values n,in a case in which the coefficient r is 1.5. As shown, the functionquickly reaches a value of approximately 2.7 and stays at that value.The outcome of the function is monotonic at that value for values of nabove approximately 9 or 10. In this state produced by the low value ofr, variation as a function of n is minimal and damps out quickly.

Returning to FIG. 2, in the range of r from approximately 3.0 to 3.4 forthe value of the coefficient of r, there are essentially two possibleoutcomes for x. In this coefficient range, the function of x tends to bebi-stable. By way of an illustrative example of a bi-stable state of thefunction of equation (1), FIG. 3B depicts the function x_(n+1), for arange to values n, in a case in which the coefficient r is 3.2.

Returning to FIG. 2, in the range of r from approximately 3.4 to 3.6 forthe value of the coefficient of r, there are essentially four possibleoutcomes for x. In this coefficient range, the function of x tends to bequad-stable, i.e. a function that exhibits essentially four regularlyrepeating outcomes. By way of an illustrative example of a quad-stablestate of the function of equation (1), FIG. 3C depicts the functionx_(n+1), for a range to values n, in a case in which the coefficient ris 3.5.

As shown in FIG. 2 the number and variances of the function x for valuesof the coefficient r increase significantly for higher values of r, sayabove 3.6 or 3.7. In the early part of this range, the function x issomewhat unstable but tends to be attracted to return in somewhatirregular manner to or near a number of recurring values, referred to asattractors. FIG. 3D illustrates an example of the function of equation(1) in which a coefficient value for r is 4.0, which produces outcomesfor x_(n+1) that vary in a somewhat unstable manner but with attractors.For a higher coefficient value, say 5.0 by way of an example, thefunction becomes completely unstable as shown by way of example in FIG.3E.

For the lighting control theory under consideration here, devices orsystems will most likely operate with a chaotic function configured in astate of a type that provides unstable with attractor type variationsanalogous to the example of FIG. 3D. However, for some purposes,quad-stable or by-stable may be used. Fully unstable would probably notbe used. Hence, for purposes discussions of further examples of lightingcontrol, we will assume use of a chaotic function in an unstable statewith attractors. If the function (1) is used as the chaotic function,the coefficient r might be set to a value that produces outcomes likethat of FIG. 3D. Attractors are results that the function tends to goback to from time to time, although not in an actual repeating pattern.In the 4.0 example of FIG. 3D, x_(n+1) tends to go back to or close tothe same minimum and maximum values in an irregular manner over time n(quasi-pattern); although the minima and maxima are not exactly thesame, the curvatures to and from maxima and minima vary, and there isnot any real exact periodicity.

The human brain also may be thought of as a chaotic system. The humanbrain tends to vary between states that are neither monostable norunstable chaotic. Instead, the brain tends to vary in a state range frombi-stable, through quad-stable up to states that may be somewhatunstable with attractors.

FIGS. 4A to 4C are function graphs useful in explaining a chaoticequation combined with a sine equation. FIG. 4A shows a chaotic functionin an unstable-with-attractors state the same as or similar to that ofFIG. 3D, over 300 units of time. The units of time may be seconds,minutes, hours, or factions or multiples of any such units, depending onthe particular lighting characteristic controlled and the purpose orobjective that is supported by the lighting control function. Forexample, different time scales may be applied for controlling intensity,color temperature, Delta_uv, etc., in the same or different lightingdevice or system. The parameter of the function shown on the verticalaxis represents magnitude of the function normalized to a range from 0to 1.

The controller 5 may be configured to apply the chaotic functiondirectly to control the relevant source output characteristic. However,in many implementations, the controller 5 may be configured to controloperation of the source(s) 4 of visible light so that the at least onecharacteristic of the visible light emitted from the source(s) 4 intothe space 1 varies in accordance with a combination of a nominalfunction over the period of time and the chaotic function. The nominalfunction may be a fixed value or a variable value. In other examples,the nominal function is a variable function added to or otherwisesuperimposed on a set value.

FIG. 4B shows a portion, in this case a half-wave or 180°, of a sinewave function. The time scale for the sine wave is the same as that usedfor the chaotic function in FIG. 4A; and again, the magnitude isnormalized to a range from 0 to 1. FIG. 4C shows a combination of thechaotic function with the sine wave. The chaotic function may becombined with the sine wave in a variety of ways. In the example, theoutcome of the sine equation is multiplied by one minus the outcome ofthe chaotic equation times a dampening parameter D. The dampeningparameter D limits the variation caused by the chaotic function. In thespecific example D=0.2.

The sine function is used here as just an easy example of a variablenominal function or variable component that may be used in combinationwith a minimum or established setting value to form a nominal function.However, many functions in nature tend to vary in a manner that can besomewhat approximated by a sine wave. FIG. 5A, for example, depicts arough approximation of the general trend (without specific values) overthe daylight hours for a nominal or normalized intensity curve fornatural sunlight. FIG. 5B shows an example of a nominal curve for colortemperature in degrees Kelvin (K) over the hours of daylight. ColorTemperature at night is ˜10,000° K. During periods of overcast or inshady areas, color temps are ˜7,500° K.

However, rather than using an approximation of the natural trend fromzero to maximum and back to zero, for artificial light, some amount ofartificial light will normally be provided at all times when the deviceor system is ON to provide light. Hence, rather than use the curve ofFIG. 4A or FIG. 4C as the lighting control function, the lighting deviceor system will typically add the function to or otherwise superimposethe function on the current setting value for the relevant lightparameter.

Using the function of FIG. 4C as the example, the function could beadded onto the otherwise normal full ON intensity value or to a somewhatlower intensity value selected by the user via a dimmer type inputprovided by user interface device 7. In this manner, the intensity ofthe output light would vary above or about the set intensity value inaccordance with the function illustrated in FIG. 4C. As a result, overthe assigned period, the actual light intensity would be the selectedintensity plus a variable amount determined by the function of FIG. 4C.

Of course, instead of or in addition to such control of intensity, acontroller 5 may control one or more other characteristics of thevisible light output from the source(s) 4, such as spectral content oflight, polarization of light, color temperature of light, andchromaticity difference (Delta_uv) of light from the Planckian locus, ina similar manner. Using color temperature as another example, thefunction of FIG. 4A reduced by application of a coefficient, saycorresponding to 10%, could be multiplied by a color temperature settingto combine the chaotic function with the nominal value function.Alternatively, to achieve a general trend more like that shown in FIG.5B, the combined function of FIG. 4B reduced by application of acoefficient, say corresponding to 10%, could be multiplied by a colortemperature setting to combine the chaotic function with the nominalvalue function.

Other techniques may be used to combine a selected function, thatincludes a chaotic function component, e.g. like the functions shown inFIGS. 4A and 4C, with a setting or other type of target value for theparticular lighting condition to which the chaotic function control isapplied.

Of course, chaotic function control components can be applied to controllighting conditions in a variety of other ways. As another example,consider next FIGS. 6A to 6C and 7. FIG. 6A is another illustration ofthe chaotic function in the unstable-with-attractors state, similar tothat shown in FIG. 4A. FIG. 6B shows another chaotic function in asimilar state but using a different timing rate. The drawings show thetwo chaotic functions over the same period, 0 to 300 time units.However, the function shown in FIG. 6A varies at a higher rate than thelower rate variation of the function shown in FIG. 6B. Although thefunctions could vary in other ways too, in this example, both areimplemented with or defined by the same equation, such as equation (1)above. To achieve the different rate functions, the functions use adifferent timing cycle or rate for n. For example, the function in FIG.6A might be controlled using n in values of seconds; whereas the FIG. Bimplementation of the function might be expressed using n in terms ofminutes or hours. Another approach to obtaining two somewhat differentchaotic functions, even if using essentially the same formula orequation is to vary the coefficient r. Of course, another exemplaryapproach would be to use different equations.

FIG. 6C shows a combination of the two chaotic functions. The chaoticfunctions may be combined in a variety of ways. In the example, assumethat the low frequency chaotic function of FIG. 6B is Cf(Lo) and thehigh frequency chaotic function of FIG. 6A is Cf(Hi). With thatnomenclature, the combined function C of FIG. 6C can be expressed asC=Cf(Lo)×(1−Cf(Hi)×D), where D is a damping coefficient. In the specificillustrated example, D in FIG. 6C is 0.2.

A function like that of FIG. 6C can in turn be used to control acharacteristic of visible light emitted from any of the light sources 4into the space 1. For example, the function of FIG. 6C could be addedonto, adjusted with a coefficient and multiplied by or otherwisesuperimposed on the regular setting value for the controlled condition.If so combined with the normal full ON intensity value or to a somewhatlower value selected by the user via a dimmer type input provided byuser interface device 7, the controlled intensity characteristic wouldvary above or about the set intensity value in accordance with thefunction of FIG. 6C. As a result, over the assigned period, the actuallight intensity would be the selected intensity combined with a variableamount determined by the function of FIG. 4C. Of course, instead of orin addition to such control of intensity, a controller 5 may control oneor more other characteristics of the visible light output from thesource(s) 4 such as spectral content of light, polarization of light,color temperature of light, and chromaticity difference (Delta_uv) oflight from the Planckian locus, in a similar manner based on acombination of a setting and a function like that of FIG. 6C.

As an alternative approach, the two chaotic functions can be combinedwith a sine wave, to produce a function like that shown in FIG. 7.Again, the sine function is used here as just an easy example of anominal function that may roughly approximate general trends ofvariations of naturally occurring lighting characteristics. Thecombination technique could combine the function of the FIG. 6C with asine wave like that of FIG. 4B in a manner similar that that used withrespect to the function of FIG. 4C. In the actual example of FIG. 7however, each chaotic function from FIGS. 6A and 6B is separatelycombined with the sine wave and then the two results are averaged toproduce the overall/combined function of FIG. 7.

Again using the nomenclature used in the discussion of FIG. 6C, the lowfrequency chaotic function Cf(Lo) of FIG. 6B is combined with the sineby multiplying the outcome of the sine equation by one minus Cf(Lo)times a dampening parameter D, to obtain a value v1. Similarly, the highfrequency chaotic function Cf(Hi) of FIG. 6A is combined with the sineby multiplying the outcome of the sine equation by one minus Cf(Hi)times a dampening parameter D, to obtain a value v2. The dampingparameters could be different; but for simplicity here, the dampingparameters are the same value D, such as 0.2. The function of FIG. 7 isthen obtained by averaging the two intermediate combinational functions,i.e. using (v1+v2)/2.

The function of FIG. 7 can be used to directly control one or more ofthe lighting characteristics, or the function of FIG. 7 can be combinedwith a setting for the characteristic(s) as in the earlier examples.Again, such a control function can be applied to light intensity and/orto one or more other characteristics of light, such as spectral contentof light, polarization of light, color temperature of light, andchromaticity difference (Delta_uv) of light from the Planckian locus.

For artificial lighting applications, chaotic functional control willnot exactly track natural lighting conditions. In some cases, theresulting variations may be quite different from those that occur in thenatural lighting. However, to promote some purposes of the illuminatedspace 1, the variation captures or adds a degree of liveliness similaror analogous to variations in natural lighting. With such arrangementsof the control algorithm implemented by controller 5, the chaoticfunction and/or the combination of a nominal function and the chaoticfunction for one or more of the controlled characteristics wouldapproximate a natural variation of the relevant characteristic(s) ofvisible light. Hence, it may be useful to consider some examples ofactual measured lighting conditions.

FIGS. 8A to 8C respectively show measured intensity (light flux, forexample, measured in foot-candles or fcd) color temperature (in degreesKelvin (K)) and chromaticity difference (Delta_uv) for a sunny day.FIGS. 9A to 9C show similar measurements taken a somewhat cloudy day.

The readings used to form the graphs in these three sets of drawingswere measured using a Minolta luminance meter arranged to collectoutside light through a window (aimed not to collect indoor artificiallight). However, the window did have some filter effect, e.g. tintingand UV protection. Also, some light reflected in from outside objects.Hence, the measurements represent light entering a room through thewindow. Photopic flux—represents amount of light—as shown in FIGS. 8Aand 9A and is a measure of light intensity. Color temperature (K) andchromaticity difference (Delta_uv) are two commonly used colorcharacteristics of light. The illustrated measurements are intended toshow relative readings that vary over time, rather than actual values.

FIGS. 8A to 8C show that flux, color temperature and Delta_uv havehighest rates of change at about the same time. The differentcharacteristics of light may be fairly monotonic over one or moresubstantial periods during the sunny day, but then each exhibits aperiod of more chaotic changes. Periods of chaotic change roughlycorrespond. In a control system, the equations for the three factors maybe coordinated in time. If the control is intended to achieve a resultsimilar to one or more of these measurement graphs, the control couldvary the coefficient r for different times of day, between a value thatproduces monotonic results and a value that produces an unstable resultwith attractors. This approach tends to liven up or put life (dynamicchange) into the controlled conditions in the space in a manner that anoccupant might perceive as similar to a pleasant sunny day outdoors.

An emulation of a cloudy day may not feel as exciting as the emulationof the sunny day, but such a control approach could be useful in somesettings or for some purposes. Hence, chaotic control functions could beused to achieve lighting variations in one or more characteristics oflight somewhat similar to those shown by way of examples in FIGS. 9A to9C.

It should be noted, however, that the concepts described here are notparticularly intended to copy or mimic exact characteristics of lightingon any particular day, e.g. the sunny day. The strategies here could beused to copy specific daylight characteristics, but typically would not.Instead, the intent of discussing the actual day light measurements isto learn and teach about relevant chaos theory based on the natural dayconditions, and then develop our techniques to add analogous componentsvia chaotic function control to dynamic change into the controlledlighting conditions in the illuminated space. Where the lighting deviceor system will varying more than one characteristic of the light, thecomponents added to vary one characteristic may be different and/orrelate to parameters of a different type of day. For example, the lightflux or intensity might vary in accordance with the function shown inFIG. 6C, whereas one or both of the color characteristics might lookmore like those from one of the days discussed above relative to FIG.8B, 8C, 9B or 9C.

In some instances outlined above, the controlled value of a lightcharacteristic would be defined by a setting value plus a variablefunction that is or includes a chaotic function, such as one offunctions discussed above relative to drawings such as FIGS. 4A, 4C, 6Ato 6C and 7. However, some or all of the variations may be limited, forexample, to insure that the variations do not deviate from settingvalues in a manner that might reduce serviceability of the lighting inthe space 1. For example, it may be undesirable for the intensity tofall below a minimum specified by a government regulatory agency or fora color characteristic to vary in a manner that might be disturbing ordistracting. Hence, the controller may be configured to limit extent ofthe variation in accordance with the chaotic function to less than orequal to a predetermined maximum amount and/or to limit rate of thevariation in accordance with the chaotic function to less than or equalto a predetermined maximum rate.

The chaotic control of light may be implemented in one or more lightingdevices 4. In the example of FIG. 1 one or each light fixture 3 is asingle independent light fixture including its own source(s) 4 ofvisible light and its own controller 5. Each such controller in turn isconfigured to implement chaotic control in a manner as outlined above.Devices like fixtures 3 illuminating the same space may control the samecharacteristic(s) of light in the same way(s), or such devices maycontrol different characteristics of light in a relatively independentmanner. However, where some coordination of variation is desirable, e.g.to have two or more characteristics have variations that are somewhatcoordinated (like those shown in FIGS. 8A to 8C or 9A to 9C), thechaotic control functions of devices illuminating one space may besynchronized or otherwise coordinated to achieve the desired results.

The present control concepts also may be implemented in lighting systemtype configurations. Such a system would include a number of lightfixtures or other types of lighting devices. In a system of fixtures,each light fixture includes one or more sources of visible light and oneor more controllers. The controllers in the light fixtures areconfigured to control operations of the sources in the fixtures in acoordinated manner to vary at least one characteristic of total visiblelight emitted by the sources into the space over the period of time atleast in part in accordance with the chaotic function. To appreciatethis later type of implementation, it may be helpful to consider thesimplified network example shown in FIG. 10. The illuminated space (orspaces) and the occupants are omitted from FIG. 10, for convenience.

Hence, FIG. 10 shows a system 8 of light fixtures 9 coupled forcommunication via a network 10. The fixtures 9 are similar to thefixtures 3 in that each of the fixtures 9 includes one or more lightsources 4 and a controller 5 and draws power from a similar powersource, represented again by connections to the AC mains 6. However, toenable communications via the network 10, each of the fixtures 9 alsoincludes a communication interface 11. The communication interface 11may be of any type suitable to provide the desired communicationcapabilities at the respective premises, e.g. bandwidth or data rate,for communication via the particular implementation of the network 10.The network 10 may be partially or entirely private, e.g. a local areanetwork (LAN) or intranet; or the network 10 may be a wide area networksuch as the public Internet. The network 10 may utilize any appropriatewired, fiber or wireless technology or combination of two or more suchtechnologies to provide communications capabilities for lighting andpossibly for other data communications at the premises of the systeminstallation and/or to devices or networks outside the premises. Basedon the configuration of the network 10, the communication interface 11may be an optical or electrical wired communication device, or thecommunication interface 11 may be an optical or radio frequency typewireless communication device. Data communication for the fixtures 9could be one-way downstream toward the fixtures 9; however, in mostcases, the network 10 and the communication interfaces 11 will supporttwo-way data communications.

In such a network environment, control and coordination amongst thenetworked fixtures 9 may be implemented in a variety of ways. Forexample, the network may merely carry signals to enable the controllers5 to synchronize their otherwise relatively independent chaotic controlfunctions. However, in most networked implementations there willactually be a higher level control function, although that higher layerfunctionality can be implemented in several different ways/places in thesystem 8. For example, one of the controllers 5 may be designated as a‘master’ controller with respect to the other ‘slave’ controllers 5. Itmay also be possible to implement the higher layer system controlfunctionality on a distributed basis, in which some portion ofprocessing resources of each of the controllers 5 is allocated to thehigher layer system control functionality while other resources of thecontrollers perform their respective individual control functions inaccordance with instructions derived collectively by the distributedhigher layer control resources.

Another approach involves use of a separate additional control unit,shown in dotted line form at 12 in the drawing. Although the higherlayer control functions of the system 8 may include a number of higherlevels of control system computers, the simple example of FIG. 10 of thesystem 8 includes a computer that serves as a central or buildingcontrol system. With regard to the controllers 5 in the light fixtures9, the computer 12 may be programmed to operate as a server, although itmay also include user interface elements such as a display and keyboard.In such an implementation, relative to the central control ‘server,’ thecontrollers 5 would be programmed or otherwise configured as clientdevices.

The central control computer 12 would receive data from the controllers5 of the light fixtures 9 via the network 10. The data, for example, mayrepresent operational states of the fixtures and/or include informationabout sensed conditions (if sensors are provided in the fixtures). Thecentral control computer 12 would process the received data and, inaccordance with its own programming, provide instructions and anynecessary data to the controllers 5 of the light fixtures 9 via thenetwork 10 to cause the system 8 as a whole to operate in a desiredmanner. Of particular note, the operations controlled in this mannerwould include various chaotic control functions of the type discussedabove.

As noted, the computer 12 may include user interface elements. Theseelements for example allow responsible personnel to review data aboutsystem operations and to change operational parameters. The computer 12may also download programming to the controllers 5 via the network 10.For high level control purposes, the exemplary system 8 also may includeone or more user terminal or client computers, for personnel of theentity operating the lighting devices 9, represented generally by thetablet computer 13 shown in the drawing. Any type of terminal, capableof communicating via the particular network 10 may be used. The terminalwould allow personnel at other locations to access the central controlcomputer 12, to perform data review and control input functions similarto those available via the keyboard and display of the computer 12.

The networked fixtures 9 could all illuminate one space; or in anetworked system 8, various groups of fixtures 9 could illuminatedifferent spaces within or about a controlled building, campus or thelike.

Although not shown, the system 8 also may include individual userinterface elements coupled to the controllers 5 or to the network 10 forlocal user inputs similar to those provided by the interface 6 in theearlier example. For example, in a multi-room venue, there might be anON-OFF switch and/or dimmer in each room to set the general intensitylevel. However, the controllers 5 of the fixtures 9 in each room wouldrespond to the central control computer 12 and would implement chaoticcontrol functions with respect to one or more characteristics of theartificial light emitted into each respective space.

The examples discussed so far have included relatively high-levelillustrations and discussions of light fixtures 3 and 9 as examples ofsuitable lighting devices. The lighting devices, whether configured asfixtures, as lamps or as other types of lighting devices, may take avariety of forms or configurations. A lighting device of the type underconsideration here, for example, may have one or more sources of any oneor more suitable types. Also, the controller may be implemented by amicro-control unit (MCU), a microprocessor, a field programmable gatearray, dedicated logic circuitry, etc. If a sensor is included, thesensor could provide feedback as to an operational state or parameter ofthe lighting device, or the sensor could measure an external conditionsuch as intensity and/or color characteristic(s) of ambient light in thespace to be illuminated. Ambient light sensing would detect light fromany uncontrolled source that may illuminate the space, such as naturallight or a lamp not incorporated into the controlled system. However,ambient light sensing may also detect at least some of the controlledartificial illumination, depending on the location, orientation and/orconfiguration of the sensor(s) used to detect ambient light in thespace.

More specific examples of lighting devices discussed below utilize solidstate type light sources. Although LEDs are discussed mainly as theexamples of solid state light sources, other solid state devices such asOLEDs may be used instead of or in combination with LEDs.

Most applications of artificial lighting involve white light, that is tosay, light that a person would typically perceive as white. In anapplication of chaotic function control intended to control onlyintensity of the light, a single intensity controllable white lightsource would be sufficient. In a solid state lighting device, forexample, a single controllable channel of one or more LEDs producingwhite light could be controlled in intensity at least in part based onthe chaotic function.

Many white LEDs today, however, do not produce a particularly goodspectral quality of light. For example, many white LEDs tend to emitlight that a person perceives as rather blue in color. Combination ofwhite LEDs with other color LEDs improves the spectral characteristic ofthe white light output of the lighting device. Two or more sets of whiteLEDs emitting white light of different color temperatures used incombination produce white of a color temperature based on the combinedcharacteristic of the different types of LEDs, which may be better thanany one of the types produces alone.

Alternatively, white LEDs can be combined with LEDs emitting somewhatmore monochromatic light of one or more colors chosen to essentiallycorrect the color characteristic of the white LEDs. For example, acombination of bluish white light LEDs with green LEDs and/or with red,amber or orange LEDs can produce combined white light of a much morepleasing color characteristic than the bluish white LEDs alone.

The somewhat more monochromatic colors of light emitted by some types ofcolored LEDs may produce light of a narrow bandwidth around thecharacteristic color wavelength. To a person, such a color appearsrelatively pure or highly color saturated. Compared to white sourcessuch as white LEDs, however, somewhat more monochromatic colors of lightemitted by some types of colored LEDs may produce light of anintermediate bandwidth around the characteristic color wavelength. Thebandwidth of light from this later type of colored LED would typicallynot be as broad as that of a white light source but would not be asnarrow as the bandwidth of the saturated color type LED. To a person,such a color appears pastel.

In a simple design, white LEDs may be combined in a single string orcontrol channel with the alternative type of white LEDS and/or with thesomewhat more monochromatic LEDs. In such an arrangement, one controlchannel would vary the intensity of light output from all of the LEDsthat together produce the white light, at least in part in accordancewith a chaotic function.

For a white lighting device intended to control a color characteristicinstead of or in addition to intensity, including the chaotic controlfunction, the device would include two or more control channels fordifferent LEDs producing light of different color characteristics. Thedifferent channels could provide RGB type control of red (R), green (G)and blue (B) LEDs. Other combinations of three or more relativelymonochromatic colors may be used.

However, most implementations for general white lighting applicationswill include at least one channel for white light production, forexample, to provide desired white light of suitable intensity in anefficient and cost effective manner. A simple two channel arrangementmight use white LEDs of two different types respectively in the twochannels. Another two channel approach might use white LEDs (of the sameor different types) in both channels, but where one or both channelshave additional somewhat more monochromatic LEDs to cause each channelto produce white light but two different color characteristics. Anothertwo-channel approach would use white LEDs in one channel (alone or withcorrective color LEDs in the same channel) together with somewhat moremonochromatic LEDs in the other channel. In these arrangements,individual control of the intensity of light produced each of the twochannels can vary the overall intensity of the light output from thewhite lighting device as well as one or more color characteristics ofthe combined light output. As discussed above, such control wouldinclude chaotic components, with respect to intensity and/or withrespect to the one or more color characteristics of the combined lightoutput.

At this point in our discussion, it may be helpful to consider aspecific example of a lighting device, again in the form of an exemplaryfixture. FIG. 11 is a functional block diagram of a light fixture 14that utilizes at least a number of solid state sources 17 and mayutilize an additional source or sources 18 of another type, such as amore conventional lamp like an incandescent lamp, a halogen lamp or afluorescent lamp. The other source and its associated driver are shownin dotted line form since they may be omitted, for example, if the solidstate sources 17 provide sufficient intensity for the particularlighting application.

In the example of FIG. 11, the fixture 14 includes a set of lightsources 41. The present example utilizes solid state sources 17.Although other solid state devices may be used, such as organic lightemitting diodes (LEDs), the example includes light emitting diodes(LEDs) as the solid state sources. The fixture 14 may utilize LEDs oftwo, three or more types, in two, three or more control channels. Forexample, as noted earlier, some fixtures may use RGB LEDs in threerespective control channels. Several of the examples outlined earlier,e.g. with two strings of white or a string for white and a string foranother non-white color may be with only two control channels. Theexample here provides at least three control channels, for three sets ofsolid state sources; and at least one of the sets of solid state sourcesin is configured to produce white light.

In the example, the first control channel C₁ includes solid statesources for white (W) light emission. Although there could be a singlewhite LED, in the example, the first control channel C₁ includes a setof LEDs 17W that together produce white light. The set of LEDs 17W couldbe LEDs of one white type or two or more types of white LEDs. However,in the example, the set of LEDs 17W includes some white LEDs and anumber of somewhat more monochromatic LEDs of one or more types, so thatthe string of LEDs 17W produces white light of a desirable colortemperature and color characteristic(s). For example, together with theactual white LEDs, the set of LEDs 17W may include some number of redLEDs, some number of orange LEDs, some number of amber LEDs, anycombination of two or all of these colors of LEDs, or combinations ofone to or more of these colors of LEDs with yet further color LEDs. Thenon-white color LEDs in the set 17W may be configured to produce pastellight of the respective color(s) or light of relatively pure saturatedcolor(s).

As noted, the example here uses three sets of LEDs in three controlchannels C₁ to C₃. Although additional sources of additional colors oflight may be provided, the example includes two no-white color sourcesin the form of LED sources of green (G) and relatively blue (B) light.Hence, the array 17 of LEDs includes a green set of LEDs 17G and a blueset of LEDs 17B. Of course, other color LED sets could be used in placeof 17G and/or 17B. The additional colors controlled through channels C₂and C₃ enable tuning of the color characteristic(s) of the combinedwhite light output of the lighting device 14 as well as chaotic controlof the color characteristic(s).

Control of the intensities of the LED outputs from channels C₁ to C₃provides control of the intensity of the combined white light output ofthe lighting device 14 as well as chaotic control of the light outputintensity. Although there may be one LED of each color, in the examples,to provide desired intensity and variability, each of the sets of LEDs17G and 17B include a number of LEDs. Each set may include a single typeof LED of the respective color, or one or both sets may include one ormore LEDs of each of a plurality of colors. For example, the set of LEDs17B may include some number of blue LEDs, some number of cyan LEDs, somenumber of royal blule LEDs, any combination of two or all of thesecolors of LEDs, or combinations of one to or more of these colors ofLEDs with yet further color LEDs generally in the blue light portion ofthe visible spectrum. The various color LEDs in the sets 17G and 17B maybe configured to produce pastel light of the respective color(s) orlight of relatively pure saturated color(s). Similar sets of LEDs but ofdifferent colors may be used as sources of additional colors of light inthe chaotic control of color characteristic(s) of the combined lightoutput of the fixture 14.

An additional source 18 of white light may be included to providesufficient intensity for a particular general lighting application. Ifprovided, the source 18 may be an additional set of LEDs similar to 17Wof the same or different overall white light characteristics, or thesource 18 may include one or more conventional devices of other types,as outlined above. Some other types of sources 18, however, such asincandescent or halogen lamps, typically are only readily controllablewith respect to intensity, although the color characteristic(s) of thelight produced by such a source may vary at relatively low intensitylevels, at relatively high intensity levels and/or from source device tosource device.

The electrical components shown in the example of FIG. 11 also include asource controller 40. The controller includes drivers corresponding tothe particular set of light sources 41. Hence, in the example, thecontroller 40 includes white, green and blue LED driver circuits 43W,43G and 43B, respectively. If the fixture includes another source 18,then the controller 40 also includes an appropriate driver 45.

The source controller 40 also includes a micro-control unit (MCU) 49. Inthe example, the MCU 49 controls the various LED driver circuits 43W,43G, 43B via respective digital-to-analog (D/A) converters 47W, 47G,47B. The intensity of the emitted light of a given LED is proportionalto the level of current supplied by the respective driver circuit. Thecurrent output of each driver circuit is controlled by the higher levellogic of the system. The D/A converter 47W controls the driver circuit43W to provide a drive current to the LEDs 17W for the white firstcontrol channel C₁ as specified by the MCU 49. Similarly, and the D/Aconverter 47G controls the driver circuit 43G to provide a drive currentto the green LEDs 17G as separately specified by the MCU 49 of thesecond control channel C₂; and the D/A converter 47B controls the drivercircuit 43B to provide a drive current to the LEDs 17B for the thirdcontrol channel C₃ as separately specified by the MCU 49; and in such anarrangement, the white light LED output may considered as anothercontrol channel C3. If provided as outlined earlier, e.g. for whitelight or for additional colors or for additional sources of the same orsimilar light types, other sets of LEDs, forming additional channels,could be controlled/operated in a similar manner.

In operation, one of the D/A converters 47 receives a command for aparticular level, from the MCU 49. In response, the converter 47generates a corresponding analog control signal, which causes theassociated LED driver circuit 43 to generate a corresponding power levelto drive the particular string of LEDs 17. The LEDs of the string inturn output light of a corresponding intensity. The D/A converter 47will continue to output the particular MCU specified driver settinglevel, until the MCU 49 issues a new command to the particular D/Aconverter 47. Thus, the particular set of LEDs 17 will continue toreceive analog current and thus will continue to output light at the setanalog level until the MCU 47 changes the applicable setting.

The example of FIG. 11 thus implements a form of analog current controlfor the LEDs 17, albeit to establish contributions to overall intensityof the combined fixture output light as well as to provide variations ofcolor characteristic(s) and/or intensity in accordance with a chaoticfunction as discussed above relative to FIGS. 1-10. Of course, othercontrol strategies may be applied to the LED channels, such as pulsewidth modulation, albeit to achieve similar outputs including chaoticfunction related variations in characteristic(s) of the fixture outputlight.

As noted, the MCU 49 controls the other light source 18, if included,via an appropriate source driver 45. For most conventional white lightsources, the driver 45 simply turns ON/OFF the source 18 and may set anintensity level for the source output, in response to a command from theMCU 49. The control routine implemented via the programming of the MCU49 would account for the inclusion of light from source 18 at any givenintensity setting, as part of its overall control of the fixture outputincluding chaotic functional variations. The MCU 49 may control thesource 18 via the driver 45 as part of the variations. In otherconfigurations, the MCU 49 may leave the driver 45 in a state so thatsource 18 provides a fairly steady output over time and implement thevariations like those discussed earlier via control of the LEDs 17 viathe converters 47R-G and the drivers 43R-G.

The MCU 49 in the example of the light fixture 14 is a microchip devicethat incorporates a processor serving as the programmable centralprocessing unit (CPU) 51 of the MCU and thus of the light fixture 14.The MCU 49 also includes one or more memories 53 accessible to the CPU51. The memory or memories 53 store executable programming for the CPU51 as well as data for processing by or resulting from processing of theCPU 51. The CPU implements the program to process data in the desiredmanner and thereby generate desired control outputs, for example, tocontrol the other elements of the fixture 14 to implement the generallighting application with chaotic function control as discussed herein.

The driver circuits, the A/D converters and the MCU receive power from apower supply 39, which is connected to an appropriate power source (notseparately shown in this drawing). The power supply 39 provides AC to DCconversion if necessary, and converts the voltage and current from thesource to the levels needed by the various electronic elements on thecontrol and communication (Ctrl./Comm.) board 37. For most lightingapplications of the type under consideration here, the power source willbe an AC line current source; however, some applications may utilize DCpower from a battery or the like. Also, the light fixture 14 may have orconnect to a back-up battery or other back-up power source to supplypower for some period of time in the event of an interruption of powerfrom the AC mains.

The electrical system associated with the fixture 14, included on theCtrl/Comm. board 37 also includes one or more communication interfaces55. If the fixture is used in a network like that of FIG. 10, onecommunication interfaces 55 would be compatible with and provide datacommunications via the particular type of network. The same or adifferent communication interface may be used to provide communicationwith any local user interface device (like the device 6 in FIG. 1) thatmay be provided in the space to be illuminated by the fixture 14.

The communication interface 55 may be an optical or electrical wiredcommunication device, or the communication interface 55 may be anoptical or radio frequency type wireless communication device. Theinterface 55 may be a one-way device or a two-way device. For purposesof our discussion, the communications interface 55 allows the MCU 49 tocommunicate with various input and control elements that may be providedin or around the illuminated space and/or via a network with otherfixtures and/or computers or terminals in a networked systemimplementation.

As noted earlier, a lighting device as discussed herein may include oneor more sensors. In the fixture 14 of FIG. 11, the device includes oneor more ambient light sensors (Sa) 31. The sensor Sa 31 providesintensity and/or color characteristic information regarding ambientlighting, as a condition input to the control logic, implemented in thisexample by the MCU 49. The sensor Sa 31 detects light from anyuncontrolled source that may illuminate the space, such as natural lightor a lamp not incorporated into the controlled system. However, ambientlight sensor Sa 31 may also detect at least some of the controlledartificial illumination from the sources 17, 18, depending on thelocation, orientation and/or configuration of the ambient lightsensor(s) Sa 31 relative to the illuminated space.

The programming of the CPU 51 configures the MCU 49 to control one ormore characteristics of the visible combined light output of the fixture14 based on the sensed ambient lighting, potentially including one ormore aspects of the chaotic function-based variation. For example, whensensing high intensity day light in the space with chaotic variations,the MCU 49 may reduce the intensity of the light output of the fixture14, reduce the magnitude of variation and/or adjust the timing of thevariations of the artificial lighting produced by the chaotic controlfunctionality. Instead of such inverse-phase control of thecharacteristics of the artificial component of the lighting in thespace, sensor responsive adjustment may produce in-phase changes. Forexample, when the sensor(s) Sa 31 indicate an increase in intensity ofdaylight in the space, the MCU 49 may increase the intensity of thelight output of the fixture 14, increase the magnitude of variationand/or change the timing of the variations of the artificial lightingproduced by the chaotic control.

The electrical components of the light fixture 14 may also include oneor more feedback sensors 35, to provide system performance measurementsas feedback signals to the control logic, implemented in this example bythe MCU 49. A variety of different feedback sensors may be used, aloneor in combination, for different applications.

A temperature sensor 35T, for example, would provide feedback regardingoperating temperature of system elements, such as one or more of theLEDs 17. If provided, the temperature sensor 35T may be a simplethermo-electric transducer with an associated analog to digitalconverter, or a variety of other temperature detectors may be used. Thetemperature sensor 35T is positioned on or inside of the fixture 14,typically at a point that is near the LEDs 17 or other source(s) 18 thatproduce most of the system heat. The temperature sensor 35T provides asignal representing the measured temperature to the MCU 49. The systemlogic, here implemented by the MCU 49, can adjust intensity of one ormore of the sets of LEDs 17 in response to the sensed temperature, forexample, to allow the MCU 49 to adjust driver current(s) appropriatelyso as to achieve programmed LED outputs even though temperatures of theLEDs may vary with time of continuous system operation.

As another example, the fixture 14 may include one or more lightresponsive feedback sensors 35L. The light feedback sensor 35L differsfrom the ambient light sensor 31 in that sensor 35L is positioned ororiented to mainly detect light produced by the sources 17 and/or 18 ofthe fixture 14 and little or no light from external sources; whereas atleast a substantial amount of light sensed by the ambient light sensormay be from one or more external sources, at least during particulartimes of day. A sensor 35L, for example, may be positioned to senselight within an optical integrating cavity that mixes the outputs fromthe LEDs 17 and the source(s) 18 to form the combined light output ofthe fixture 14. A light sensor 35 may sense intensity and/or a colorcharacteristic of the light produced in or by the system 14 or 11B.Intensity feedback, for example, may be used to adjust drive current tothe LEDs 17. Color characteristic feedback may be used to adjust thedrive currents to combinations of LEDs 17 to adjust the characteristicof the combined light output of the fixture 14. Feedback from the lightsensor 35L may also be used to adjust timing of light emissions, forexample, to help insure synchronization of chaotic variations by anumber of similar fixtures illuminating the same space.

A fixture 14 may be implemented using a variety of optical andelectrical housing elements. For example, it was mentioned brieflyearlier that the fixture may utilize an optical integrating cavity tocombine light from the various sources 17 and/or 18 to form the lightoutput of the fixture 14. Other types of optical mixers may be usedinstead of the optical integrating cavity. Various reflectors ordeflectors may be added to direct the output light in a mannerappropriate for a particular illumination application. The fixturehousing may facilitate a flush ceiling or wall mount, may allow thefixture to hang from a wall or be mounted on but extending out from awall, etc. As noted in earlier discussions, however, even the fixtureconfiguration is shown and described by way of example, since theconcepts of chaotic functional control of lighting can be implemented inother types of lighting devices.

In a lighting device that utilizes a programmable device in thecontroller, such as a microprocessor or an MCU like 49, the relevantcontrol functionality is defined by the executable instructions thatprogram the CPU of the programmable device. The chaotic function controlcan be programmed into such a device as part of the initial constructionor installation of a lighting device. Alternatively, the chaoticfunction control may be retrofitted into an existing fixture, device orsystem, for example, by updating the control program for the relevantcontroller(s). Generally, the discussion above has focused on techniquesand equipment for implementing the chaotic function control of lighting.However, where a programmable controller is used, the chaotic functioncontrol may also be embodied in the control program for the device.

In this regard, a program product or ‘article of manufacture’ may takethe form of a machine or computer readable medium in combination withthe relevant program instructions embodied in the medium. Non-transitoryforms of such a medium, for example, include various types of memoriesthat may be used in the controllers to store programs for use by theCPUs as well as various types of disk storage media that might be usedto hold the programming before downloading through a network forinstallation in a particular controller.

For information about additional examples of white lighting fixtures andassociated controllers that may be programmed or otherwise configured inaccordance with the discussion herein, attention may be directed to U.S.Utility patent application Ser. No. 13/218,148, Filed Aug. 25, 2011,entitled “TUNABLE WHITE LUMINAIRE,” the disclosure of which is entirelyincorporated herein by reference.

The concepts outlined above are susceptible to a wide range of variationwithin the general range of the exemplary teachings herein. As anexample of variants of the concepts outlined above, the user interfaceprovided in the occupied/illuminated space may offer a greater degree ofindividual control. The specific examples described earlier providedON/OFF and/or dimming type examples. The interface may also allowcontrol of color characteristic(s) of the illumination in the space.Also, for some installations, it may be preferable to provide controlover the chaotic function variations. For example, an occupant in oneroom may prefer less variation in lighting than an occupant in anotherroom. Hence, the user interface might allow occupants in each of therooms to individually control the chaotic function related variations inthe different rooms.

As noted earlier, the technologies discussed in the examples may beapplied to control lighting of spaces intended for other biologicaloccupants in addition to or instead of humans. Examples of applicationwith respect to other biological life forms include lightingapplications for plants and animals, aquatic life forms, insects, etc.The lighting may help to increase growth and yield. As another example,the lighting may also help to contain animals or drive away animals orinsects.

It will be understood that the terms and expressions used herein havethe ordinary meaning as is accorded to such terms and expressions withrespect to their corresponding respective areas of inquiry and studyexcept where specific meanings have otherwise been set forth herein.Relational terms such as first and second and the like may be usedsolely to distinguish one entity or action from another withoutnecessarily requiring or implying any actual such relationship or orderbetween such entities or actions. The terms “comprises,” “comprising,”“includes,” “including,” or any other variation thereof, are intended tocover a non-exclusive inclusion, such that a process, method, article,or apparatus that comprises a list of elements does not include onlythose elements but may include other elements not expressly listed orinherent to such process, method, article, or apparatus. An elementproceeded by “a” or “an” does not, without further constraints, precludethe existence of additional identical elements in the process, method,article, or apparatus that comprises the element.

Unless otherwise stated, any and all measurements, values, ratings,positions, magnitudes, sizes, and other specifications that are setforth in this specification, including in the claims that follow, areapproximate, not exact. They are intended to have a reasonable rangethat is consistent with the functions to which they relate and with whatis customary in the art to which they pertain.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

What is claimed is:
 1. A lighting device, comprising: at least onecontrollable source of visible light configured to illuminate a space tobe utilized by one or more biological occupants; and at least onecontroller coupled to the at least one source of visible light, whereinthe at least one controller is configured to control operation of the atleast one source of visible light so as to vary at least onecharacteristic of visible light emitted from the at least one sourceinto the space over a period of time at least in part in accordance witha chaotic function.
 2. The lighting device of claim 1, wherein the atleast one controller is configured, to vary the operation of the atleast one source of visible light in such a manner that the at least onecharacteristic of the visible light emitted from the at least one sourceinto the space varies over the period of time at least in part inaccordance with the chaotic function, so as to effect perception by theone or more occupants in a manner that promotes an objective purpose ofthe space when occupied.
 3. The lighting device of claim 1, wherein thelighting device is a single light fixture including the at least onesource of visible light and the at least one controller.
 4. A systemcomprising a plurality of the lighting devices of claim 1, wherein thecontrollers in the lighting devices are configured to control operationsof the sources in the lighting devices in a coordinated manner to varythe at least one characteristic of total visible light emitted by thesources into the space over the period of time at least in part inaccordance with the chaotic function.
 5. The system of claim 4, furthercomprising: a network, wherein: each of the lighting devices furthercomprises a communication interface configured to enable communicationvia the network; and the communications via the network facilitates thecontrol operations of the sources in the lighting devices in saidcoordinated manner to vary the at least one characteristic of totalvisible light emitted by the sources into the space over the period oftime at least in part in accordance with the chaotic function.
 6. Thelighting device of claim 1, wherein the at least one characteristic ofvisible light that varies includes one or more light characteristicsselected from the group consisting of: intensity of light, spectralcontent of light, polarization of light, color temperature of light, andchromaticity difference (Delta_uv) of light from the Planckian locus. 7.The lighting device of claim 1, wherein the at least one characteristicof visible light that varies comprises intensity of light and at leastone color characteristic of light.
 8. The lighting device of claim 7,wherein the at least one color characteristic of light includes one ormore color characteristics selected from the group consisting of:spectral content of light, color temperature of light, and chromaticitydifference (Delta_uv) of light from the Planckian locus.
 9. The lightingdevice of claim 1, wherein: the at least one source of visible lightcomprises at least one first source configured to emit visible light ofa first color characteristic and at least one second source configuredto emit visible light of a second color characteristic different fromthe first color characteristic, and the at least one controller isconfigured to control the first and second sources to vary a colorcharacteristic of combined visible light emitted by the sources into thespace over the period of time at least in part in accordance with thechaotic function.
 10. The lighting device of claim 9, wherein the variedcolor characteristic of combined visible light emitted by the sourcesinto the space is a color characteristic selected from the groupconsisting of spectral content of light, color temperature of light, andchromaticity difference (Delta_uv) of light from the Planckian locus.11. The lighting device of claim 1, wherein the at least one controlleris further configured to limit extent of the variation in accordancewith the chaotic function to less than or equal to a predeterminedmaximum amount.
 12. The lighting device of claim 1, wherein the at leastone controller is further configured to limit rate of the variation inaccordance with the chaotic function to less than or equal to apredetermined maximum rate.
 13. The lighting device of claim 1, whereinthe at least one controller is configured to control operation of the atleast one source of visible light so that the at least onecharacteristic of the visible light emitted from the at least one sourceinto the space varies in accordance with a combination of a nominalfunction over the period of time and the chaotic function.
 14. Thelighting device of claim 12, wherein the combination of the nominalfunction and the chaotic function approximates a natural variation of atleast one characteristic of visible light.
 15. The lighting device ofclaim 1, wherein the at least one controller is further configured tocontrol operation of the at least one source of visible light so thatthe at least one characteristic of the visible light varies inaccordance with the chaotic function in a state that is unstable withattractors.
 16. The lighting device of claim 1, wherein the chaoticfunction comprises a mathematical expression that determines thevariation of the at least one characteristic in a dynamic manner thatappears random or lacking in order.
 17. The lighting device of claim 16,wherein the expression is dynamic and highly sensitive to an initialcondition.
 18. A method, comprising steps of: operating an electricallydriven source to emit visible light, to illuminate a space to beutilized by one or more biological occupants; and controlling avariation of at least one characteristic of the visible light emittedfrom the source over a period of time at least in part in accordancewith a chaotic function.
 19. The method of claim 18, wherein thevariation in accordance with the chaotic function is configured toeffect perception by the one or more occupants in a manner that promotesan objective purpose of the space when occupied.
 20. The method of claim18, wherein a coefficient of the chaotic function has a value thatconfigures the chaotic function in a state that is unstable withattractors, for at least part of the period of time.
 21. The method ofclaim 18, wherein the controlling step comprises varying the at leastone characteristic of the visible light from the source in accordancewith a combination of a nominal function over the period of time and thechaotic function.
 22. The method of claim 21, wherein the combination ofthe nominal function and the chaotic function approximates a naturalvariation of at least one characteristic of visible light.
 23. Themethod of claim 18, further comprising: sensing a characteristic ofambient light in the space, wherein the controlling of the variation ofat least one characteristic of the visible light emitted from the sourceis at least partially responsive to the sensed characteristic of ambientlight in the space.
 24. An article of manufacture, comprising anon-transitory machine readable medium and instructions embodied in themedium for configuring a programmable controller of a lighting device toimplement the method of claim
 18. 25. The method of claim 18, whereinthe chaotic function comprises a mathematical expression that determinesthe variation of the at least one characteristic in a dynamic mannerthat appears random or lacking in order.
 26. The method of claim 25,wherein the expression is dynamic and highly sensitive to an initialcondition.